The present invention relates to a rubber-reinforced thermoplastic resin and a rubber-reinforced thermoplastic resin composition. More particularly, it relates to a rubber-reinforced thermoplastic resin which has been reinforced with an acrylic rubber-like polymer and which can provide the molded articles having excellent impact resistance, weather resistance and surface appearance; and a rubber-reinforced thermoplastic resin composition comprising the said rubber-reinforced thermoplastic resin and other non-diene rubber-reinforced thermoplastic resin, which composition is capable of providing the molded articles having a high-level balance of impact resistance, weather resistance and surface appearance. The rubber-reinforced thermoplastic resin and the rubber-reinforced thermoplastic resin composition according to the present invention can be used for the parts, chassis, housings, etc., of various industrial products such as OA equipment, household electrical appliances, products in the electric and electronic fields, miscellaneous goods, sanitary products, vehicles, etc.
ABS resins using diene rubber-like polymers as rubber moiety, AES resins using ethylene-propylene rubber, and ASA resins using acrylic ester rubber have been widely known as rubber-reinforced thermoplastic resins.
The diene rubber used in the said ABS resins as rubber moiety has an unsaturated double bond in the molecular chain. The molded articles of these ABS resins have such disadvantage that when these articles are exposed to sunlight in outdoor use, there may take place oxidation or severance of molecular chain at the unsaturated double bond portion of the rubber moiety, causing discoloration and deterioration of properties of the articles. Therefore, outdoor use of the molded articles comprising ABS resins has been limited. Certain improvement for such use may be provided by adding an ultraviolet absorber, light stabilizer, antioxidant or such to the resin, but this can not provide total elimination of the said defect of the ABS resins.
In an attempt to overcome the said defect of ABS resins, many proposals have been made on the techniques using saturated rubber containing no unsaturated bond in the molecular chain. AES and ASA resins are superior to ABS resins in respect of weather resistance, and they have already been put to practical use as a molding material for the products for outdoor use. The molded articles using AES resins, however, are inferior to those of ASA resins in visual appearance, while ASA resins are inferior to AES resins in impact strength. So, there has been a demand for providing a weather resistant resin which has high impact strength and also excels in surface appearance of its molded products. When the expression “excels in surface appearance” is used here, it means that the molded article has a surface having excellent gloss, free of flow marks and segregation, and also having good colorability.
For the improvement of qualities of the said ASA resins, methods are known in which a diene rubber is incorporated in an acrylic rubber-like polymer, or an ABS resin is blended in an ASA resin. The molded products obtained by utilizing these methods are indeed improved in impact resistance, but they are unsatisfactory in surface appearance and weather resistance.